Many athletes and non-athletes utilize weight-training exercises to build strength and/or bulk, to prevent injury, to recover from injury and/or to improve overall condition and appearance. Over the past several decades or so, exercise machines of various types and configurations have been designed for facilitating such weight training exercises. Exercise machines have been developed for many different purposes. Exercise machines can be specifically configured for use in the home, in health clubs, in physical therapy environments or the like. More specifically, exercise machines can be configured to exercise several different parts of a body (e.g., most exercise machines configured for use in the home) or can be configured to provide exercise that is targeted at a specific muscles group (e.g., legs, chest, arms, back, etc.) Examples of such muscle group specific exercise machines (i.e., those typically used in health clubs and physical therapy environments) include leg presses, bench presses, arm curl machines, squat machines and the like.
The ability to exercise mover muscles, which are large muscles and/or muscle groups that exert force in a manner that exhibit strength, is one design consideration of nearly all exercise machines. Predominant (e.g., large) muscles within muscle groups commonly referred to as quadriceps, hamstrings and the calves are examples of mover leg muscles. Muscles within muscle groups commonly referred to as biceps, triceps and deltoids are examples of mover arm muscles. Rotator cuff muscles and hip joint muscles are examples of stabilizer muscles. In some respects, it is an easy task to design an exercise machine to activate such mover muscles. For example, force application devices such as bench press hand gripping members, leg press foot platens, and the like, which maintain a machine designated orientation while force is being exerted thereon, result in mover muscle groups being readily activated during force exertion. The exercise machine controls and/or stabilizes placement of the force application device during force application, which causes mover muscles to be the primary muscles engaged.
Development of mover muscles is the desired and intended objective of many weight training programs and associated exercises. Such strength training exercise uses resistance to strengthen and condition the musculoskeletal system, thereby improving strength, tone and endurance of mover muscle groups. However, there are instances where it is necessary and/or desirable to activate stabilizer muscles and/or core or bulk muscles that act in a stabilizing manner, as opposed to or in combination with mover and core muscles. For example, in weight training, fitness training and rehabilitation therapy, it is beneficial to activate such stabilizer muscles to strengthen them, develop/redevelop physical coordination and the like. Stabilizer muscles are muscles that provide for alignment and positional control of interconnected skeletal structures such as for example interconnected skeletal structures at the wrists, ankles, hips and shoulders.
Training for neuromuscular stability and coordination is sometimes referred to functional training, balance training, or unstable training, and will be referred to hereinafter as unstable training. It is believed that unstable training (i.e., training with instability within a force application device) challenges the neuromuscular system to a greater extent compared to training on stable (e.g., fixed) platforms. Training with instability within a force application device can increase proprioceptive (i.e., body positioning) demands and stress the core muscles that are important for stability and balance.
Typical strength and power training on a stable surface elicits fast twitch muscle fibers. Because using unstable surface movement requires the movement to be performed in a slower, more controlled manner, these exercises often predominantly target slow-twitch stabilizing and postural muscles. One of the goals of this type of training is dynamic joint stabilization, which refers to the ability of the kinetic chain (muscles, nervous, and skeletal systems) to stabilize a joint during movements. One example of dynamic joint stabilization is the rotator cuff stabilizing the head of the humerus on the glenoid fossa (shoulder blade) while performing a push-up. Another example of dynamic joint stabilization is the gluteus medius (i.e., outer thigh) and adductor complex (i.e., inner thigh) stabilizing the hip when performing a squat. Still another example of dynamic joint stabilization is the posterior tibialis and peroneus longus (i.e., calf muscles and tendons) stabilizing the foot and ankle complex when performing a calf raise.
In research published in the Canadian Journal of Applied Physiology (February 2005, Anderson K, Behm DG) the objective of the study was to determine the differences in electromyographic (EMG) activity of the soleus (SOL=calf), vastus lateralis (VL=outer thigh), biceps femoris (BF), abdominal stabilizers (AS), upper lumbar erector spinae (ULES), and lumbo-sacral erector spinae muscles (LSES) while performing squats of varied stability and resistance. Stability was altered by doing a squat exercise movement on a Smith brand squat machine, a free squat, and while standing on two balance discs. Fourteen male students performed the movements using each of the three exercise protocols. Activities of the SOL, AS, ULES, and LSES were highest during the unstable squat (i.e., on the balance discs) and lowest with the Smith Machine protocol.
Therefore, an apparatus that is configured for causing stabilizer muscles to be selectively activated and exerted during exercise of corresponding core and mover muscle groups would be advantageous, desirable and useful.